All ABC News broadcasts and platforms are delivering the latest updates on the ongoing investigation as well as the stories of those who witnessed the tragic attack -

" World News with Diane Sawyer" will have the latest on the investigation during a special one-hour editionof the broadcast which will include reports from ABC's team in Boston as well as Chief National Correspondent Byron Pitts, Chief Global Affairs Correspondent Martha Raddatz, Chief White House Correspondent Jonathan Karl, Senior Justice Correspondent Pierre Thomas, and Senior National Correspondent Jim Avila. - UPDATE: Diane Sawyer will speak to Dr. Dave King, a trauma surgeon at Mass General in Boston. In addition Boston MayorThomas Menino and former New York City Mayor Rudy Giulini will speak with Sawyer.

" Nightline" will originate from Boston with Terry Moran anchoring from there. The program will feature reports by Brian Ross and John Donvan.

On Monday, two small but powerful bombs exploded at the finish line of the Boston Marathon and 24 hours later no one has claimed responsibility for what authorities have labeled a "terrorist" attack. FBI says investigation will be worldwide. "We will go to the ends of the earth to find subject or subjects responsible for this despicable crime," said FBI Special Agent in Charge Richard DesLauriers.

For the latest information on ABC's coverage of this story click here.